The invention relates generally to magnetic disk drive storage systems, and relates more particularly to a key plate system which protects against insertion of an inappropriate disk drive carrier into a system.
Many challenges face the designer of a magnetic disk drive storage system. In a typical system, there is an enclosure with a number of slots into which disk drive carriers may be inserted. A typical system may have fourteen slots. The disk drive carriers each carry a disk drive. The disk drives work together to provide a highly reliable storage system with a high density of storage. Among the issues are concerns about constructive interference arising out of vibrations in drives of the system and about provision of cooling air. In any of these systems, it is important to design the system so that a user will not inadvertently insert a carrier into the enclosure that is not supposed to be inserted into the enclosure. For example, a product line of disk drive storage systems may include systems that differ from one to the next in important ways. It is desirable to have a standardized enclosure across the product line, and to have standardized disk drive carriers, yet it would be undesirable if a user could insert a carrier from one system into the enclosure of a different system. This may happen because the equipment is supplied to several OEM (original equipment manufacturer) customers, or may happen because the same product line platform is used for various electrical interfaces (e.g. SCSI versus fibre channel, or 2 gigabit fibre channel versus 1 gigabit fibre channel).
One prior-art approach to this problem is to use keying pins in the electrical connectors of the carriers and in the electrical connectors of a backplane located at the rear of the enclosure. This approach has the advantage that keyed connectors are well known and many keyed combinations are able to be configured in a typical keyed-connector scheme. In a system that only has one or two slots requiring keying, this approach can be advantageous, and the high cost of such connectors can be accommodated.
But where the number of slots is large, a keyed-connector scheme is unduly expensive due to the number of such connectors. A keyed-connector system typically has small piece parts that must be assembled into the connectors. There is the danger that of the dozen or more connectors in a drive storage system, one or more connectors might be incorrectly keyed due to incorrect assembly of the keying piece parts. The manufacturer can try to catch such mistakes through testing (for example, inserting each keyed connector into a test jig) but such testing is time-consuming and uses up some of the insertion life of the connector. Worse, there are some keying errors (such as failure to insert a blocking part) that might not be detected by test insertions of a mating connector in a test jig.
A further difficulty with many keying schemes is that they require real estate. A connector-based scheme for example requires an allocation of real estate in a planar area that might otherwise have provided more conductors in a connector. Other keying schemes, such as schemes in which a printed circuit board card edge fits into an edge connector, require control of the width of the card edge. A disk drive carrier enclosure system, due to its dense construction, has very little real estate available for keying schemes. Indeed the width of the carrier is limited because of the need to fit as many carriers as possible into a standard enclosure width (defined by standard equipment rack dimensions).
Another prior-art approach is to have a keying scheme in a single plane within the rails of the carriers. This is usually done with tabs or screws aligning with a matching plate embedded within the enclosure, but only within one plane.
There is thus a great need for a keying system for use in a disk drive storage system that overcomes these difficulties. Such a system would need to avoid some or all of the error-prone insertion of keying piece parts. It would need to provide a straightforward way of keying all slots, a dozen or more in number, identically, preferably in a single assembly step. It would need to have a small overall parts count. Such a scheme must accommodate the necessarily narrow drive carriers of a storage system without using up real estate that is needed for other design purposes. Finally, it should be able to provide assembly customization of at least six combinations at minimal cost, and should be generalizable to a scheme offering more than six combinations.
An enclosure is shaped with a plurality of opposed pairs of first and second guides, the first guides all substantially coplanar within a first plane, the second guides all substantially coplanar within a second plane. Each pair of guides defines a respective plane, the respective planes of the pairs of guides all parallel to each other, each pair of guides separated by a respective spacing, each pair of guides shaped to receive a respective planar carrier by insertion in a first direction along the pair of guides. The enclosure is shaped to receive a key plate parallel to the first plane and intersecting the first guides, said key plate having a plurality of feature areas, each feature area corresponding to a respective plane of one of the pairs of guides, each feature area presenting a predetermined pattern of barriers to movement in the first direction, the barriers disposed at at least two locations along the first direction. The enclosure includes a plurality of electrical connectors corresponding to respective pairs of first and second guides, each connector disposed between ends of its respective first and second guides and positioned perpendicular thereto.